A. Field of Invention
This invention pertains generally to the in-circuit functionality testing of active linear components; and more specifically to a device and procedure to provide for the in-circuit measurement and testing of general purpose operational amplifiers (op-amps).
B. Description of the Background
For this invention, in-circuit test or measurement refers to a printed circuit board test technique which, through the use of various isolation techniques, performs "pin checks" and "gross functionality tests" on individual operational amplifiers regardless of the specific circuit configuration or the effects of surrounding components. "Pin checks" refer to tests specifically designed to verify appropriate electrical activity on all device pins (the physical connections to the devices). "Gross functionality tests" are more comprehensive than pin checks and refer to tests designed to verify the basic function of the part in addition to simply verifying pin activity. Neither test provides a full functionality testing of the op-amp component specifications.
The proliferation of active linear electronic components, i.e. integrated circuits designed to perform such analog functions as amplification, voltage comparison, etc. has rendered standard in-circuit fault detection techniques obsolete, and created manufacturing and quality control problems for printed circuit board assemblies utilizing these devices. Central to this problem is the class of components known as operational amplifiers. Operational amplifiers are used in a multitude of amplification, integration, differentiation, and summing applications within general purpose analog designs. Conventional analog in-circuit test techniques (designed primarily to test passive components) will not suffice as a means of performing a comprehensive in-circuit functionality test of active components such as operational amplifiers. In addition, analog functional tests (those designed to test the operational amplifier and surrounding components as a functional block) are difficult to implement and do not provide good fault isolation diagnostics. As a result, printed circuit board assemblies utilizing operational amplifiers have been difficult to test, due to the previously intractable problem of programmatically generating in-circuit tests for these components independent of the effects from surrounding circuitry.